Home television receivers generally do not have a power isolation transformer because of cost considerations and therefore they have a ground system which is connected directly to the AC power supply. This presents a problem for connecting a home TV to a home computer, video game, or other video signal source system which requires isolation from the AC power supply. Optical isolation of the signal source and receiving systems is one solution, but coupling of video signals is difficult because the signal carries a large amount of information and therefore requires a wideband coupler. It is important that a video coupler be adapted to receive industry standard signals and provide an output signal which complies with those standards.
Present techniques of video coupling include the use of a wideband signal transformer, the use of an integrated coupler device such as the Hewlett-Packard 6N136 plus amplifiers using discrete circuitry components, and the use of an isolating power transformer in the TV display. As mentioned above, the use of a wideband transformer adds materially to the cost of the TV set. Further, the bandwidth over which such transformers can operate efficiently is generally insufficient to the demands of the situation. Finally, the use of discrete circuit components has a number of problems associated with it, such as relatively high assembly costs, noise pickup, limited bandwidth, and instability due to parasitic capacitances.